Function PHP - Validate Date, returns TRUE if the date given is valid; otherwise returns FALSE.

is_date_valid.php

<?php
/**
 * Validate Date
 * 
 * @return boolean Returns TRUE if the date given is valid; otherwise returns FALSE.
 */
function is_date_valid( $date, $format = 'Y-m-d H:i:s'){
	if( ! isset( $date ) || isset( $date ) && ! is_string( $date ) )
		return false;

	$date_time  = DateTime::createFromFormat( $format, $date );
	$is_invalid = (bool) ( $date_time && $date_time->format( $format ) == $date );

	return $is_invalid;
}